In this paper, nitrogen‐coordinated boroxines are exploited for the fabrication of self‐healing and recyclable polymer composites with enhanced mechanical properties. The 3D polymer networks ...cross‐linked with nitrogen‐coordinated boroxines are first synthesized through the trimerization of ortho‐aminomethyl‐phenylboronic acid groups at the terminals of poly(propylene glycol) (PPG) chains, and subsequently, the mechanically robust polymer composites are fabricated by utilizing the complexation of nitrogen‐coordinated boroxine‐containing PPG (N‐boroxine‐PPG) with poly(acrylic acid) (PAA) and hydrogen‐bonding interactions between them. The N‐boroxine‐PPG is soft with a tensile strength of 0.19 MPa, whereas the tensile strengths of N‐boroxine‐PPG/PAA composites can be tailored to range from 1.7 to 12.7 MPa by increasing the PAA contents in the polymer composites. It is revealed that the amine ligands can facilitate the formation and dissociation of nitrogen‐coordinated boroxines at room temperature. Moreover, the reversibility of nitrogen‐coordinated boroxines and hydrogen‐bonding interactions enable multiple cycles of healing and recycling of the damaged N‐boroxine‐PPG/PAA composites. The healed and recycled N‐boroxine‐PPG/PAA polymer composites regain most of their mechanical strength.
Nitrogen‐coordinated boroxines are exploited for the fabrication of mechanically robust self‐healing and recyclable polymer composites by the complexation of nitrogen‐coordinated boroxines‐crosslinked poly(propylene glycol) with poly(acrylic acid). Because of the high reversibility of nitrogen‐coordinated boroxines, the as‐prepared polymer composites exhibit excellent self‐healing and recycling capacity. The polymer composites can retain their original mechanical robustness even after multiple cycles of healing and recycling process.
The first direct and selective 3,6‐di‐thiolation and 3,6‐di‐selenylation of carbazoles using diaryl disulfides/diselenide as the sulfur/selenium source were demonstrated. This simple, general, and ...efficient method could deliver a wide range of 3,6‐di‐sulfenyl‐carbazoles and 3,6‐di‐selenyl‐carbazoles from readily available starting materials with high regioselectivity in an easily‐operated one‐step reaction via a Ag/K2S2O8‐mediated protocol.
The first synthesis of 3,6‐di‐sulfenyl‐carbazoles and 3,6‐di‐selenyl‐carbazoles was successfully achieved in a simple and efficient one‐step reaction.
The first enantioselective synthesis of pyrrolyl-substituted triarylmethanes has been accomplished using a novel imidodiphosphoric acid catalyst, which is derived from two (R)-BINOL frameworks with ...different 3,3'-substituents. This strategy was also expanded to the synthesis of bis(indolyl)-substituted triarylmethanes with high enantioselectivities, which could only be obtained with moderate ee values in previous reports. These two efficient Friedel-Crafts alkylation processes feature low catalyst loading, broad functional group compatibilities, and the potential to provide practical pathways for the synthesis of enantioenriched bioactive triarylmethanes.
We report an iron‐catalyzed divergent synthesis of alkylated indoles based on precise control of the activation sites on indoles through the selection of catalysts. Using indoles and styrenes as ...starting materials, 3,5‐di‐alkylated indoles could be prepared selectively and directly for the first time by treating with a catalytic amount of Fe(OTf)3 and 3‐alkylated indoles were achieved exclusively by adding a catalytic amount of γ‐cyclodextrin as the cocatalyst with Fe(OTf)3. This simple method was demonstrated with 52 examples with high yields and broad functional group compatibilities.
A general, efficient and regioselective protocol has been developed for the synthesis of trifluoromethylated bis(carbazolyl)methanes. This metal‐free transformation proceeds smoothly under air ...atmosphere and features broad scope for both reaction partners. This method could also be extended to the synthesis of difluoromethylated and chlorodifluoromethylated bis(carbazolyl)methanes.
Cool cats: 1,1′‐Bi‐2‐naphthol and vaulted 3,3′‐biphenanthrol‐type bisphosphorylimides enabled the atom‐economical and highly enantioselective Friedel–Crafts reaction between indoles and N‐tosylimines ...with a low catalyst loading (see scheme). A very small amount of 4‐(dimethylamino)pyridine (DMAP) suppressed the bisindole side product efficiently. The ortho‐substituted aldimine substrates performed excellently in this catalytic system.
A simple and efficient methodology for the first synthesis of tri- and di-fluoromethyl-bis(indolyl)methanols has been demonstrated through a one-pot Friedel–Crafts-type acylation–alkylation of ...readily available indoles and fluorinated acids. This simple protocol was successfully performed under metal-, additive-, toxic-solvent-, and protective-gas-free conditions, and delivered a wide range of tri- and di-fluoromethyl-bis(indolyl)methanols in moderate to high yields. Notably, this reaction can tolerate diverse vital and reactive functional groups. Furthermore, this one-pot Friedel–Crafts-type acylation–alkylation can be readily expanded to the gram scale with no obvious decrease in the yield, demonstrating its high application potential.
In this paper, a wideband eight-element multiple-input multiple-output (MIMO) antenna array for 5G smartphone applications is presented. Each antenna is composed of a dual-arm tortuous monopole ...radiating element with a double-stub tuner and an open slot on the ground plane. Tuning stub microstrip lines are utilized to improve impedance matching. The operating bandwidth of the single antenna element is from 3200 to 6000 MHz with three resonant frequencies. The operating bandwidth covers the 5G new radio (NR) bands (n77/n78/n79) and the WLAN-5GHz band. The isolation of the proposed MIMO antenna array is above 10 dB in the entire operating band without any isolation elements. Furthermore, the proposed MIMO array was manufactured and measured. The measured results validate that the MIMO antenna array has a wide 6-dB impedance bandwidth from 3.2 to 6 GHz and the isolations are all more than 10 dB. The total efficiency ranges from 38% to 83%. The above results show that this MIMO antenna array can support 5G applications in smartphones.
The prognostic factors and optimal treatment for the elderly patient with glioblastoma (GBM) were poorly understood. This study extracted 4975 elderly patients (≥ 65 years old) with histologically ...confirmed GBM from Surveillance, Epidemiology and End Results (SEER) database. Firstly, Cumulative incidence function and cox proportional model were utilized to illustrate the interference of non-GBM related mortality in our cohort. Then, the Fine-Gray competing risk model was applied to determine the prognostic factors for GBM related mortality. Age ≥ 75 years old, white race, size > 5.4 cm, frontal lobe tumor, and overlapping lesion were independently associated with more GBM related death, while Gross total resection (GTR) (HR 0.87, 95%CI 0.80-0.94, P = 0.010), radiotherapy (HR 0.64, 95%CI 0.55-0.74, P < 0.001), chemotherapy (HR 0.72, 95%CI 0.59-0.90, P = 0.003), and chemoRT (HR 0.43, 95%CI 0.38-0.48, P < 0.001) were identified as independently protective factors of GBM related death. Based on this, a corresponding nomogram was conducted to predict 3-, 6- and 12-month GBM related mortality, the C-index of which were 0.763, 0.718, and 0.694 respectively. The calibration curve showed that there was a good consistency between the predicted and the actual mortality probability. Concerning treatment options, GTR followed by chemoRT is suggested as optimal treatment. Radiotherapy and chemotherapy alone also provide moderate clinical benefits.
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